QUALITY MONITORING OF SHENZHEN’S COASTAL WATERS BY SATELLITE AND ITS SPATIOTEMPORAL VARIATION
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摘要: 近年来,近岸海域富营养化与赤潮暴发问题日益突显,对粤港澳大湾区核心城市深圳的可持续发展构成重要挑战。为有效解决这一问题,了解深圳近岸海域水质和赤潮暴发事件的时空动态变化至关重要。利用MODIS卫星传感器数据,建立了水质遥感反演和赤潮自动化提取模型,首次揭示了深圳海域水质关键参数与赤潮暴发的时空格局,并分析了主要驱动因素。研究结果显示,深圳市辖海域赤潮年均影响范围为300.50 km2,年均暴发频次为2.38次。2015—2022年,赤潮暴发覆盖面积每年增长约为6.7%。珠江口和深圳湾海域的悬浮泥沙浓度和叶绿素a浓度高于大鹏湾和大亚湾,并呈增长趋势。尽管珠江口东部海域富营养化程度高,赤潮暴发频次却较低,主要受河口悬浮泥沙的影响。而水质较好的大鹏湾和大亚湾赤潮暴发频次较高,且呈逐年上升趋势,这可能与氮磷比的变化有关。南澳、葵涌与坝光海域的氮磷比含量需重点关注,并对其陆域片区的面源污染源进行综合评估,研究结果可为稳步推进深圳及其周边海域环境治理修复和考核管理提供重要基准信息。Abstract: In recent years, coastal eutrophication and the resulting red tide occurrences have emerged as pressing environmental concerns, posing significant challenges to the sustainable development of Shenzhen, a key city in the China Great Bay Area. Addressing this issue effectively hinges upon a comprehensive understanding of the spatiotemporal dynamics of water quality and red tide outbreaks in Shenzhen's coastal regions. This study utilized the data from the Moderate Resolution Imaging Spectroradiometer(MODIS) to establish models for remote sensing inversion of water quality parameters and automated extraction of red tide occurrences. It has unveiled, for the first time, the spatiotemporal patterns linking key water quality parameters in Shenzhen's coastal waters with red tide outbreaks and analyzed the primary driving factors. Our findings revealed an average annual affected area of red tide occurrence spanning approximately 300.50 km2 within Shenzhen's jurisdictional waters, occurring on average 2.38 times annually. Between 2015 and 2022, the annual growth rate of red tide outbreak coverage was approximately 6.7%. Suspended sediment and chlorophyll-a concentrations in the Pearl River Estuary and Shenzhen Bay surpassed those in Dapeng Bay and Daya Bay, exhibiting an increasing trend. Despite the high eutrophication level in the eastern part of the Pearl River Estuary, the frequency of red tide outbreaks remained relatively low, primarily influenced by estuarine suspended sediments. In contrast, regions with superior water quality, such as Dapeng Bay and Daya Bay, experienced higher red tide frequencies that exhibited an annual increasing trend, potentially linking to the variation in nitrogen-phosphorus ratios. The study underscored the imperative need to target nitrogen-phosphorus ratios in the Nan'ao, Kuichong, and Baguang areas and undertook a comprehensive assessment of non-point pollution sources in their terrestrial zones. This information can serve as baseline information crucial for continuously advancing environmental governance, restoration efforts, and management evaluations concerning Shenzhen and its surrounding maritime areas.
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Key words:
- Shenzhen nearshore waters /
- water quality parameter /
- red tide /
- temporal and spatial changes /
- MODIS
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